The securement of an underlayment such as roofing felt or the like to a roofing substrate has, for many years, utilized fasteners which incorporate a disk or cap surrounding the shank of the nail, directly below the nail head, for providing improved gripping engagement with the underlayment to minimize tearing of the underlayment at the point of engagement with the nail. The cap (sometimes referred to as a pressure plate) associated with the nail is sometimes constructed of metal, although more frequently is constructed of plastic. One example of such cap is illustrated by U.S. Pat. No. 5,407,313 owned by the Assignee hereof. The use of a plastic cap in conjunction with a securing nail has provided significantly improved gripping performance with respect to securement of the underlayment to the substrate. Such fasteners, often referred to as cap nails, have encountered user resistance, however, since they are not suitable for use with conventional powered nailing systems.
In an effort to improve on the above, the Assignee has developed a powered nailing device which feeds not only nails but also plastic caps so as to permit the nail to be driven through the cap during use of the device, and hence greatly improve the speed with which cap nails can be used for securing an underlayment. In such device, a large plurality (such as several hundred) of plastic caps are joined together in adjacent side-by-side relationship to define an elongate strip, which strip is formed into a spiral coil and is supported on the nailing device for feeding caps to the nailing zone. The strip of caps, in this prior development, utilizes an elongate adhesive tape for joining the caps together, which tape is broken or severed between adjacent caps during the nailing operation. While use of adhesive tape for creating the strip provides a desirable operational arrangement, nevertheless using tape for forming the strip is somewhat difficult and in-efficient. Also, the tape has a tendency to stick to other objects.
Another known powered cap nailing device is illustrated by U.S. Pat. No. 5,947,362, which device also utilizes an elongate strip of joined plastic caps formed into a spiral coil, in conjunction with a separate nail magazine, so that the caps and nails are fed into a nailing zone for permitting the nail to pierce the cap during a nailing operation. The coiled strip of caps associated with the nailing device of the U.S. Pat. No. 5,947,362 joins adjacent caps of the strip utilizing a small plastic web extending between the peripheries of adjacent caps, which web is severed during the nailing operation. However, the process associated with the forming of this strip is less than desirable.
More specifically, the elongate cap strip of the type disclosed in the U.S. Pat. No. 5,947,362 is believed formed from a plurality of molded strip segments which each contain a plurality of caps disposed in aligned side-by-side relationship. The mold for forming the strip segment has a number of full size cavities corresponding to the number of caps in the strip segment, and at one end has a partial cavity which forms only a partial cap. After the strip segment has been molded, resulting in a partial cap or plug at one end of the strip, the mold is then opened and the strip segment is advanced so that the partial cap at one end of the strip is then positioned in the cap cavity disposed at the other end of the mold cavity. The mold is then closed and a further injection cycle is carried out, which results in injection of additional material around the partial cap so as to permit formation of a complete cap at one end of the mold cavity, and an additional partial cap is formed at the other end of the molded strip segment. This sequential molding and joining process then continues so that a significant number of strip segments are joined together to define the elongate strip, which can then be suitably packaged, such as wound into a spiral coil. With this arrangement, however, it has been observed that the cap formed in the end cavity in which the partial cap is positioned and overmolded results in problems such as flash around the cavity, as well as surface defects and disfiguration due to the overmolding involved. In addition, inasmuch as one strip segment is almost immediately removed from the mold and then joined to the next molded strip segment, this hence requires additional cooling and hence additional time in order to accomplish the molding of each strip segment, and also requires handling of the strip segments prior to their having adequately cooled, whereby such handling is more difficult and the strip segments are more susceptable to damage. This process also requires additional space and equipment, as well as handling, inasmuch as the strip segments are immediately and sequentially joined together to define the strip as the individual segments are sequentially molded.
In addition to the use of pressure caps for nails as disclosed above, the Assignee has also developed an automated stapling device which, in conjunction with a coiled strip of pressure caps, permits a stapling system to be used for securing the underlayment to the roof substrate, while at the same time utilizing a pressure cap in conjunction with a staple so as to provide improved securement performance. Such device is illustrated in U.S. Pat. No. 6,478,209, owned by the Assignee hereof. This device utilizes plastic caps which are generally similar to those utilized for nails, and while the legs of the staple do successfully penetrate the cap so as to permit securement to the roof substrate, nevertheless it is believed that improved performance can be achieved by providing a modified plastic cap for use specifically with staples.
Accordingly, it is an object of this invention to provide an improved process for creating an elongate strip of interconnected plastic roof securement caps, which strip can be suitably coiled, and which process overcomes disadvantages associated with prior processes for creating such strips, as briefly discussed above.
More specifically, the present invention relates to an improved forming process wherein an elongate strip segment containing a significant number of sidewardly adjacent caps are simultaneously formed in a mold with adjacent caps being joined through a molded plastic web. The cap formed at one end of the strip segment has a small recess formed therein, and the cap formed at the other end of the strip segment has a web joined thereto which in turn joins to a small molded connector part. Several such strip segments can be simultaneously molded in a common mold. The strip segments are removed from the mold for cooling to permit a fast cycle time in the mold, and the cooled individual strip segments can, at any time thereafter, and at any desired location, be joined together to create an elongate strip of desired length. For the latter purpose the strip segments are generally aligned and the connecting part associated with one end of a first strip segment is interfitted into the recess associated with the other end of a second strip segment to create a fixed joining of adjacent strip segments in generally aligned relationship. In a preferred variation the connecting part on one strip segment, when fitted in the recess of the next strip segment, is sonically welded to create a permanent joinder of the aligned strip segments. The joined strip segments can then be suitably packaged, such as wound into a coil. The forming of the individual strip segments hence greatly facilitates cooling and subsequent handling, it also facilitates the securement of adjacent strip segments at remote or different locations if desired so as to facilitate intermediate storage or handling of the strip segments, it also permits the mold to be of minimal complexity while at the same time minimizing the mold cycle time, and it permits all of the caps to be uniformly formed of desired quality without encountering undesired or excessive flash or surface irregularities.
It is also an object of the invention to provide an improved plastic pressure cap configured specifically for use with a staple for permitting securement of an underlayment to a roofing substrate, which plastic cap and its cooperation with the staple is believed to provide improved performance with respect to the ability of the staple legs to properly penetrate the cap and effect desired securement with the substrate.
More specifically, the improved plastic cap for use with a staple incorporates a raised center part which, in a conventional manner, depresses downwardly when engaged with a staple for securement with the underlayment. The raised center portion of the pressure cap, however, has an elongate recess formed in the upper surface thereof, which recess opens downwardly and terminates in a generally flat bottom wall, with the height of the recess being such that the base of the staple can be wholly accommodated in the recess and not protrude thereabove when the staple and cap are secured to the substrate. The recess in the elongate direction will typically have a dimension which is at least about twice the recess width so that the staple, when applied by an automated device such as illustrated by Assignee's U.S. Pat. No. 6,478,209, can be readily positioned so as to extend down into the recess and penetrate the bottom wall thereof, thereby ensuring that the base of the staple will be properly disposed within the recess and hence the plastic wall surrounding the recess will effectively shelter the staple base from the overlying roof, particularly if the overlying roof is of metal.
Other objects and purposes of the invention will be apparent to persons familiar with constructions and processes related to the present invention upon reading the following specification and inspecting the accompanying drawings.
Certain terminology will be used in the following description for convenience in reference only, and will not be limiting. For example, the words “upwardly”, “downwardly”, “rightwardly” and “leftwardly” will refer to directions in the drawings to which reference is made. The word “top” or “upper” will be used to refer to the side of the cap through which the fastener, such as a staple, is typically driven, this being the upper side illustrated in FIGS. 3–7, and the word “bottom” will be used to reference the opposite side of the cap, namely that side which engages the roof underlayment. Said terminology will include the words specifically mentioned, derivatives thereof, and words of similar import.